Secretion of anterior pituitary hormone undergoes the control of peripheral hormone secreted from target organs for the respective hormones and by secretion-accelerating or -inhibiting hormone from hypothalamus, which is the upper central organ of anterior lobe of pituitary (in this specification, these hormones are collectively called "hypothalamic hormone"). At the present stage, as hypothalamic hormones, nine kinds of hormones including, for example, thyrotropin releasing hormone (TRH) or gonadotropin releasing hormone {GnRH: sometimes called as LH-RH (luteinizing hormone releasing hormone)} are confirmed their existence (cf. Seirigaku 2, compiled by M. Iriku and K. Toyama, published by Bunkohdo, p610-618, 1986). These hypothalamic hormones are assumed to show their actions via the receptor which is considered to exist in the anterior lobe of pituitary (cf. ibid), and observational studies of receptor genes specific to those hormones, including cases of human, have been developed (Receptor Kiso To Rinsho, compiled by H. Imura, et al., published by Asakura Shoten, p297-304, 1993). Accordingly, antagonists or agonists specifically and selectively acting on these receptors control the action of hypothalamic hormone and controlling the secretion of anterior pituitary hormone. As the results,they are expected to be useful for prophylactic and therapeutic agents of anterior pituitary hormone dependent diseases.
Leuprorelin acetate [Fujino et al., Biological and Biophysical Research Communications, Vol.60, 00.406-413, 1974); Oliver, R. T. D. et al., British Journal of Cancers, Vol.59, p.823, 1989; and Toguchi et al., Journal of International Medical Research, Vol.18, pp. 35-41], which is a highly potent derivative of gonadotropic hormone-releasing hormone, one of the hypothalamic hormones, (hereinafter sometimes abbreviated as GnRH) [Schally A. V. et at., Journal of Biological Chemistry, Vol. 246, pp.7230-7236, 1971; and Burgus, R. et al., Proceeding of Natural Academic Science, USA, Vol.69, pp278-282, 1972], by administration of multiple doses, lowers release.production of gonadotropic hormone in pituitary, causing lowering of reactivity on gonadotropic hormone is spermary and ovary to suppress secretion of testosterone and estrogen. Leuprorelin acetate has, therefore, been known to show antitumor activity on such hormone-dependent cancers as exemplified by prostate cancer, and has been widely used in the clinical field. Leuprorelin acetate has been widely used clinically also as a therapeutic agent of e.g. endometriosis and precocious puberty. The high antitumor activity of leuprorelin acetate is assumed to be due to its high resistance, as compared with natural GnRH, against protease,and to high affinity to GnRH receptor causing desensitization of GnRH due to decrease in number of receptors. However, as leuprorelin acetate is an ultra-agonist on GnRH receptor, it has been known that, immediately after the first administration, a transient aggravation accompanied with the rise of serum testosterone concentration due to pituitary-gonadotropic action (acute action) is observed. Circumstances being such as above, GnRH antagonistic drugs which are expected to have substantially the same therapeutic effects as described above but not to cause the above-mentioned transient pituitary-gonadotropic action (acute action) have been desired. As compounds having such GnRH antagonistic activity, a number of compounds including, for example, derivatives of GnRH such as straight-chain peptides, (U.S. Pat. Nos. 5,140,009, 5,171,835), cyclic hexapeptide derivatives [JPA S61(1986)-191698] or bicyclic peptide derivatives [Journal of medicinal chemistry, Vol.36, pp.3265-3273, 1993]. These compounds are, however, all peptides, which leave many problems including, for example, dosage forms, stability of drugs, durability of actions and stability on metabolism. For solving these problems, orally administrable GnRH antagonistic drugs, especially non-peptide ones, are strongly desired. At the present stage, however, no report on non-peptide GnRH antagonistic drugs has been made.
An object of the first embodiment of the invention lies in providing novel compounds having excellent gonadotropic hormone releasing hormone antagonistic activity as well as excellent gonadotropic hormone releasing hormone antagonistic agents.